silicone hydrogel contact lens

SILICONE HYDROGEL CONTACT LENSES

Optom Muhammed Shareef EK Bejan Singh Eye Hospital

What is silicone hydrogel CL..??

• Soft contact lenses were made possible in the 1960s and 1970s These were called "hydrophilic gels" or simply "hydrogels.

• Silicone Hydrogel contact lenses are literally a breath of fresh air for eye care patients. Brought onto the market in 1999,

• Silicone hydrogels are the latest in a line of developments aimed at increasing the oxygen permeability (increased comfort, longer wear and better eye health), wettability (better comfort)

• Silicone has higher oxygen permeability, allowing more oxygen to pass

• They are healthier than conventional soft lenses because they allow up to 6 times more oxygen to pass through them and increased oxygen transmission results in better overall eye health.

Characteristics of Silicone Hydrogel Lenses

1. Modulus2. Oxygen Permeability3. Wettability

Modulus

• When we speak about the characteristics of silicone hydrogel materials, the term, “modulus” is often used.

• It describeshow well a material resists deformation.• Most silicone hydrogel lenses have a relatively high

modulus compared with hydrogels.• The ease-of-handling and excellent durability imparted

by the higher modulus of silicone hydrogels make them a good choice for patients who have had difficulty inserting hydrogels.

•

Oxygen Permeability

• Hydrogels have a maximum Dk value under 40• Current silicone hydrogels range from 60 (Dk/t

86) for Vistakon’s ACUVUE® ADVANCE™ to 140 (Dk/t 175) for CIBA Vision’s NIGHT & DAY®.

• All current silicone hydrogel lenses except the ACUVUE® ADVANCE™ have Dk/t values of at least 100 and are FDA-approved for extended wear. The ACUVUE® ADVANCE™ lens, with a Dk/t value of 86, is approved for daily wear only

• Clinical signs of oxygen deficiency with hydrogel materials include

1. conjunctival injection2. Limbal redness3. Neovascularization4. Corneal edema Etc….

Types of Silicone Hydrogel Contact Lenses

• There are three types of silicone hydrogel lenses available. They are spherical, toric, and bifocal.

• Patients can choose from daily disposals, six-day extended wear, two-week daily wear, or thirty-day continuous and daily wear lenses.

Materials

• These come with technical names such as 1. Galyfilcon2. Senofilcon3. Comfilcon4. Enfilcon5. Lotrafilcon

• Silicone hydrogel contact lenses sometimes are erroneously called silicon hydrogel lenses.

• Silicon is a very common mineral. In fact, ordinary sand is composed primarily of silicon dioxide.

• Silicone is the name of a group of flexible, plastic-like materials that contain silicon, carbon, oxygen and other chemicals.

• In addition to its use to increase the oxygen permeability of contact lenses, silicone is used to make breast implants, medical tubing and other medical devices

Advantages of silicone hydrogel CL..

• More resistance to protein deposits• Less drying of the lenses• Lower risk of eye infection• Easier handling due to increased rigidity of

material• And much lower incidence of complications

with extended wear use (overnight wear)

Indications

• People who wear their lenses for more than 12 to 14 hours a day.

• Kids and teenagers who tend to routinely over wear their lenses.

• Since the Focus Night & Day as well as the PureVision lenses are approved for 30 days of continuous wear, they can be considered as a useful alternative for people contemplating refractive surgery.

• Especially useful in the following types of patients: people with high prescriptions

• Those whose eyes show signs that they require more oxygen

• Wearers who experience end of day discomfort

• Dryness• Redness with their conventional soft lenses

• All contact lenses reduce the amount of oxygen that reaches the front surface of the eye to some degree.

• When the cornea's oxygen supply is significantly reduced — a condition calledhypoxia

• Hypoxia-related eye problems became a significant issue in the 1990s when extended wear contact lenses first gained popularity.

• Silicone hydrogel lenses were introduced in hopes of decreasing hypoxia-related problems and increasing the safety of both daily wear and extended wear of soft contact lenses.

Brands..• The current brands of spherical silicone

hydrogel lenses available, in order of highest oxygen transmissibility to lowest, are:

• Ciba Focus Night & Day which is approved for 30 day continuous wear

Coopervision Biofinity

• Coopervision Avaira; at this time approved only for daily wear and two week replacement.

• Vistakon's Acuvue Oasys which is approved for 2 week daily wear use or 6 night extended wear and is designed to be more wettable than the others and is therefore beneficial for people who have dry eyes

• Ciba's O2 Optix which is approved for 6 days continuous wear or 2 weeks daily wear

• Bausch & Lomb's PureVision which is approved for 30 days continuous wear

• Vistakon Acuvue Advance which is a 2 week disposable lens and has not yet been approved for extended wear.

Toric SH CL• There are also currently two toric silicone

hydrogel lenses on the market:Bausch & Lomb PureVision Toric is a silicone hydrogel toric lens approved for 30 days extended wear use

• Acuvue Advance For Astigmatism – currently approved as a 2 week daily wear lens.

Ciba Airoptix for astigmatism

Contra indication..??

Contra indication

• Silicone hydrogels may not be the lens of choice for all patients

• These lenses are generally more expensive than non-silicone lenses

• So a more price conscious consumer may not prefer this option.

• In some wearers, the silicone material tends to attract more lipid deposits, which may cause blurred vision and discomfort

• There are some cases where a patient is not able to adapt well to the more rigid silicone material, which may result in some minor defects to the corneal integrity.

• These complications are rare and generally the health advantages and increased comfort that most wearers experience.

Thank You…!!